Re: [lwip-users] UDP send example

[Jon Bean]

Patrick, I managed to get it to work finally. But I had to just assign 
the addr values rather than using the mem copy. Using mem copy I ended 
up with a different value in addr.

Thanks for all your help.

Jon

udp_addr.addr = addr->addr;

On 10/07/2020 14:37, Patrick Klos wrote:
> On 7/10/2020 9:04 AM, Jon Bean wrote:
> > Patrick, you are correct its an issue with the addr. I think its 
> > because I am assigning it in the rx function, but then the addr 
> > pointer is destroyed so I end up with a NULL pointer. Is there some 
> > way to copy the address in LWIP? I had some issues with the code you 
> > sent. I had to use addr->addr as it didn't like addr.ip4.addr.
> >
> > Thanks
> >
> > Jon
>
> You don't want a pointer to the IPv4 address.  You want to copy the 
> structure to your own copy.  You should probably just do something 
> like this:
>
> Declare the global udp_addr structure:
>
>         ip_addr_t udp_addr;     (instead of "ip_addr_t *udp_addr;)
>
> Then in your receive code:
>
>         memcpy((void *)&udp_addr, (void *)&addr, sizeof(ip_addr_t));
>
> Now you have a real copy of the originating IP address.
>
> Your send code might want to check the udp_addr.addr has actually been 
> set before you try to use it?
>
> I've been using LwIP with the TIVA platform over 5 years (maybe 7?) 
> and it has been working quite well for me.  I'm sure you'll be able to 
> get things working without too much (more) trouble.
>
> Patrick
>
> > On 10/07/2020 13:37, Patrick Klos wrote:
> > > On 7/10/2020 8:19 AM, Jon Bean wrote:
> > > > Hi Patrick
> > > >
> > > > That solved the crashing problem thanks. Problem is that I never 
> > > > receive the data. If I send from the receive function it works 
> > > > fine. But doing it from the LWIP timer handler it never arrives. 
> > > > The udp_sendto function returns without any errors, just no data 
> > > > arrives. Any idea why?
> > > >
> > > > Thanks
> > > >
> > > > Jon
> > >
> > > I would double check exactly what's in your udp_addr and udp_port 
> > > variables.
> > >
> > > Add this line (or something equivalent) to your eth_udp_rx() function:
> > >
> > >         printf("eth_udp_rx: addr=%08x port=%04x udp_addr=%08x 
> > > udp_port=%04x\n",
> > >                         addr.ip4.addr, port, udp_addr.ip4.addr, 
> > > udp_port);
> > >
> > > (what version of LwIP are you using?  I still have 1.4.1 on my TIVA 
> > > Launchpad)
> > >
> > > See if (make sure) you get the same numbers to start with.
> > >
> > > Patrick
> > >
> > > > On 10/07/2020 13:06, Patrick Klos wrote:
> > > > > On 7/10/2020 6:44 AM, Jon Bean wrote:
> > > > > > Hi
> > > > > >
> > > > > > I am trying to setup an application on a Texas Instruments TIVA 
> > > > > > micro controller. What I am trying to do is first receive a UDP 
> > > > > > packet from a pc to the board. I then want to be able to send 
> > > > > > packets back when I have data to send. I have managed to do this 
> > > > > > using the UDP echo example. But this send a packet back when it 
> > > > > > gets a response. I tried calling my send function from a loop in 
> > > > > > main. But it just crashed. I asked on the TI form and was told I 
> > > > > > need to call the udp_sendto function from an interrupt. I cahnged 
> > > > > > the code so that it is aclled from the LWIP timer handler. But 
> > > > > > its still crashing. Can anyone see an issue with the code below 
> > > > > > or have a working example? Thanks
> > > > > >
> > > > > > The udp_addr and udp_port vars are what I set when I get the 
> > > > > > receive packet from the host. The new_udp_pcb is created in my 
> > > > > > setup function.
> > > > > >
> > > > > > void eth_udp_tx()
> > > > > > {
> > > > > >     struct pbuf *p;
> > > > > >     uint8_t buf[4];
> > > > > >
> > > > > >     p = pbuf_alloc(PBUF_TRANSPORT, 4, PBUF_POOL);
> > > > > >     p->len = 4;
> > > > > >     p->tot_len = 4;
> > > > > >     p->payload = buf;
> > > > > >
> > > > > >     if (p)
> > > > > >     {
> > > > > >         udp_sendto(new_udp_pcb, p, udp_addr, udp_port);
> > > > > >         pbuf_free(p);
> > > > > >     }
> > > > > > }
> > > > >
> > > > > I'm pretty sure it's a bad idea to replace the point in p->payload 
> > > > > with your own pointer.  That might be your entire problem?  Copy 
> > > > > your data to the payload buffer provided and try that.
> > > > >
> > > > > Also note, you don't have to set p->len or p->totlen - LwIP 
> > > > > handles that for you in most or all cases.
> > > > >
> > > > > If that doesn't work, here is the code I use to send a simple UDP 
> > > > > packet: (udp_data is an array of bytes)
> > > > >
> > > > >             p = pbuf_alloc(PBUF_TRANSPORT, sizeof(udp_data), 
> > > > > PBUF_RAM);
> > > > >             if (p)
> > > > >             {
> > > > >                 memcpy(p->payload, udp_data, sizeof(udp_data));
> > > > >                 i = udp_sendto(udp_pcb, p, &broadcast_address, 
> > > > > my_ip_port);
> > > > >                 if (i != ERR_OK)
> > > > >                 {
> > > > >                     printf("Got error %d when sending UDP 
> > > > > packet!\n", i);
> > > > >                 }
> > > > >                 else
> > > > >                 {
> > > > >                     if (debug)
> > > > >                         printf("Sent (%d.%03d microseconds 
> > > > > [%d])\n", subtick/120, ((subtick%120)*1000)/120, subtick);
> > > > >                 }
> > > > >                 pbuf_free(p);
> > > > >             }
> > > > >             else
> > > > >             {
> > > > >                 printf("Couldn't allocate a pbuf!!\n");
> > > > >             }
> > > > >
> > > > > Good luck!
> > > > >
> > > > > Patrick Klos
> > > > > Klos Technologies, Inc.
> > > >
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